Coronary Artery Disease Risk Assessment Coronary artery disease (CAD) occurs when the coronary arteries, or the arteries that bring blood to the heart muscle, become hardened and narrowed. The arteries harden and narrow because of a buildup of plaque on their inner walls. This is called atherosclerosis. Significant narrowing of the coronary arteries can reduce blood to flow to the heart. This limits the amount of oxygen the heart receives and can lead to angina, heart failure, irregular heart rhythm, an...